Nexus Between Human Thermoregulation and Cardiovascular Functions—A Preliminary Simulation for a Moderate Variation of Temperature

Abstract

Though the interaction between cardiovascular functions and thermoregulation is enormously complex yet immensely important, very little effort to date has been spent to simulate it from a system point of view. The present work aims at simulating the mutual interaction of human thermoregulation and cardiovascular functions by combining simple models of these two systems. While for thermoregulation, a lumped parameter multi-node model has been developed, a SIMULINK-based approach of electrical analogy has been taken for the cardiovascular system. These two models are coupled by different physiological and control actions, represented by well-established correlations. Three case studies have been conducted. In the first case, thermoregulation of a healthy human being is considered for a prescribed temperature cycle of moderate variation. Under heat stress, cardiac output increases by a joint effect of heart rate and stroke volume while under the cold condition, the variation of the cardiac output is less and is primarily governed by the heart rate. For the case of a reduced ejection fraction of the left ventricle, though there is a notable decrease in skin blood flow, negligible variation in skin and core temperature is observed. In the case of acute aortic stenosis, it is found that the blood pressure falls severely from its normal level causing hypotension and is further aggravated even under moderate heat stress. Such a situation might have further consequences like heat stroke. Finally, the limitations of the present study have been highlighted and suggestions have been made for further improvement.